Pressure sensor having a rotational response to the environment

ABSTRACT

Methods and systems of the invention are directed to a pressure sensor that includes a substrate, a first conductive plate, and a second conductive plate. The substrate is formed of a material having a low coefficient of thermal expansion (CTE). The first conductive plate is formed of a material having a CTE that is higher than the CTE of the substrate, and is attached to a first surface of the substrate. The second conductive plate is rotatably connected to the substrate through a hinge, and includes a portion that is adjacent to the first conductive plate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.12/026,757, filed on Feb. 6, 2008, which in turn claims the benefit ofpriority to U.S. Provisional Application Ser. No. 60/899,627, filed Feb.6, 2007, the entire contents of each of which are incorporated herein intheir entirety by reference.

FIELD

The present invention relates generally to temperature transducers andmore particularly to transducers that shift a frequency of a reflectedsignal based on a response to temperature.

BACKGROUND

In operations, piping can extend hundreds or thousands of feet belowground to a well through a harsh environment. Devices have been used formonitoring downhole conditions of a drilled well so that efficientoperation can be maintained. These downhole conditions includetemperature and pressure, among others. A temperature sensor implementedin this environment should be robust and configured to operate withinthe potentially difficult environmental conditions. Likewise, atemperature sensor in this environment should be relatively insensitiveto changes in pressure.

SUMMARY

A temperature sensor in accordance with an embodiment includes asubstrate formed of a material having a first coefficient of thermalexpansion, wherein the substrate has a first mount portion. Thetemperature sensor also includes a first conductive plate formed of amaterial having a second coefficient of thermal expansion that is higherthan the first coefficient of thermal expansion. The first conductiveplate is attached to a first surface of the substrate and the firstconductive plate has a first contact portion. A second conductive plateof the temperature sensor has a second mount portion rotatably connectedto the first mount portion of the substrate, the second conductive platebeing adjacent to the first conductive plate.

A temperature sensor in accordance with an embodiment includes a firstconductive element configured and arranged to generate a mechanicalforce in response to a temperature condition. The temperature sensoralso includes a second conductive element configured and arranged tovary a capacitance in response to the mechanical force, the secondconductive element having a first portion and a second portion such thatthe second conductive element establishes a distance between the firstportion and the first conductive element via a rotation of the secondportion about an axis of the first conductive element. The first portionof the second conductive element is adjacent to a surface of the firstconductive element, and the second portion of the second conductiveelement is rotatably attached to a mounting portion of the firstconductive element.

A method in accordance with an embodiment include measuring temperaturein an enclosure using a system having a capacitive sensor with a firstconductive plate having a high coefficient of thermal expansion and asecond conductive plate rotatably attached to the first conductiveplate. The method includes generating a signal having a predeterminedfrequency, shifting the frequency of the generated signal based on arotation of the first conductive plate or second conductive plate due tothe temperature of the enclosure, and correlating the frequency shift toa temperature value.

A system in accordance with an embodiment includes a receiver in anenclosure, a sensor, configured and arranged to modulate theelectromagnetic signal based on a temperature in the enclosure, and aprocessor configured and arranged to correlate the modulated signal to atemperature value. The sensor includes first conductive elementsconfigured and arranged to generate a mechanical force in response to atemperature condition. The sensor also includes a second conductiveelement rotatable about the first conductive element in response to themechanical force, the second conductive element having a first portionand a second portion such that the second conductive element establishesa distance between the first portion and the first conductive elementvia a rotation of the second portion about an axis of the firstconductive element. The first portion of the second conductive elementis adjacent to a surface of the first conductive element, and the secondportion of the second conductive element is rotatably attached to amounting portion of the first conductive element.

DESCRIPTION OF THE DRAWINGS

Embodiments will be described in greater detail in reference to thedrawings, wherein:

FIG. 1 illustrates a first temperature sensor in accordance with anembodiment;

FIG. 2 illustrates a second temperature sensor in accordance with anembodiment;

FIG. 3 illustrates a system for measuring the temperature of anenclosure in accordance with an embodiment; and

FIG. 4 is a flow chart that illustrates a method of measuring thetemperature of an enclosure in accordance with an embodiment.

DETAILED DESCRIPTION

FIG. 1 is a schematic illustration of an embodiment directed to atemperature sensor 100. The temperature sensor 100 includes a substrate102, a first conductor plate 104, and a second conductor plate 106.

The substrate 102 includes a first substrate layer 108 and a secondsubstrate layer 110. The first substrate layer 108 is formed from aninsulating material, such as Maycor™ ceramic, for example, having a lowcoefficient of thermal expansion. The first substrate layer 108 contactsa bottom surface of the first conductor plate 104. The second substratelayer 110 contacts a bottom surface of the first substrate layer 108,and is connected to the second conductor plate 106 through a hinge 112.The second substrate layer 110 is formed from a material having acoefficient of thermal expansion that is lower than the coefficient ofthermal expansion of the first substrate layer 108. In embodiments, thesecond substrate layer 110 may be formed from a material such as Invar®,for example. One of ordinary skill in the art will appreciate that thematerials that make up the first substrate layer 108 and the secondsubstrate layer 110 are not limited to Maycor™ and Invar®, respectively,and may be formed of any material that achieves the desired response.

The first conductor plate 104 is arranged on a top surface of the firstsubstrate layer 108, and is formed of a metal having a coefficient ofthermal expansion that is greater than the coefficient of thermalexpansion of the first substrate layer 108. Aluminum is a suitable metalfor use as the first conductor plate 104, however one of ordinary skillin the art will appreciate that the first conductor plate 104 is notlimited to this selection. Conductors having a linear coefficient ofthermal expansion greater than about 10·10⁻⁶ l/K, and in particular,metals having such a coefficient, are well-suited to use in thisembodiment. Examples include many types of steel, copper and aluminum,though the invention is not limited to these examples. The firstconductor plate 104 includes a non-conductive portion 104 a. Thenon-conductive portion 104 a is a portion of the first conductor plate104 that is anodized or otherwise processed to be non-conductive. Thenon-conductive portion 104 a includes a tip portion that contacts thesecond conductor plate 106 such that a fulcrum is established.

The second conductor plate 106 includes a first leg 106 a and a secondleg 106 b. The first leg 106 a extends in a plane that is substantiallyparallel to the first conductor plate 104. The first leg 106 a and thefirst conductive means plate 104 are arranged such that a gap (G) ofapproximately ten one thousandths of an inch (0.010″), or lesser orgreater, is established therebetween. The second leg 106 b is integratedwith the first leg 106 a and extends in a plane that is substantiallyperpendicular to the direction of the first leg 106 a. In an embodiment,the first leg 106 a and the second leg 106 b can be configured in anL-shape, for example, but may also be configured in any manner thatachieves the desired response. The second leg 106 b includes a hinge 112to which the second substrate layer 110 is connected, and contacts thenon-conductive portion 104 a of the first conductive means plate 104.

The hinge 112 that is securely mounted to the second leg 106 b andincludes a metal sleeve and a pin.

The temperature sensor 100 may also include a mounting block 114 that isattached to a bottom surface of the substrate 102. The mounting block114 may include recessed portions for mounting the temperature sensor100 to a rigid structure.

The mounting spring 116 connects an end of the mounting block 114 to thesecond leg 106 b of the second conductor plate 106. The mounting spring116 provides a restorative force that enables the gap (G) of thetemperature sensor 100 to return to its original spacing at ambienttemperatures. A positive stop, not shown, may be employed to avoid thespring enlarging the gap beyond a selected starting distance.

The temperature sensor 100 includes fasteners 118 and 122 that securethe substrate 102, the first conductor plate 104, and the mounting block114 to one another. The fastener 118 extends from a top surface of thefirst conductor plate 104 to an interior portion of the substrate 102.The second fastener 122 extends from a bottom surface of the mountingblock 114 to an interior portion of the substrate 102. The fasteners 118and 122 can be implemented through a number of known fastening devices,such as a screw, tangs, pins, or rivets, for example. The fastener 118may be adjusted along the length of the first conductive means plate 104to a point where the fastener 118 does not effect the spacing of the gap(G).

A terminal 120 is arranged on the first conductor plate 104. Theterminal 120 is secured to the first conductor plate 104 through thefastener 110. The terminal 120 extends from an outer end of the firstconductor plate 104. The terminal 120 is formed of conductive materials,such as a welded wire for example, and provides a connection to anexternal circuit.

During operation, as the temperature of the surrounding environmentincreases, the first conductor plate 104 expands in a lengthwisedirection. This expansion of the first conductor plate 104 causes aforce to be applied to the first leg 106 a of the second conductor plate106 at the fulcrum of the non-conductive portion 104 a. The forcecreated by the expansion of the first conductor plate 104 and the secondconductor plate causes one of the conductor plates to rotate about thehinge 112 and adjust the spacing of the gap (G). The gap (G) may beadjusted in a range of approximately 0.010″ to 0.030″, or lesser orgreater as desired. Whether the first conductor plate 104 or the secondconductor plate 106 rotates about the hinge 112 is determined by whichof the aforementioned components is mounted to a rigid structure.

For example, in an embodiment, the second conductor plate 106 may beattached or mounted to a rigid structure (not shown) through the secondleg 106 b. As the external temperature increases, the degree ofexpansion undergone by the first conductor plate 104 determines anamount of force that the first conductor plate 104 applies to the secondleg 106 b of the second conductor plate 106 at the fulcrum of thenon-conductive portion 104 a. Because the second conductor plate 106 issecurely mounted to a rigid structure, the amount of force applied bythe first conductor plate 104 determines the angle at which the firstconductor plate 104 (through its attachment to the substrate 102)rotates about the hinge 112.

In some embodiments, the mounting plate 114 is securely attached ormounted to a rigid structure. As the external temperature increases, thedegree of lengthwise expansion of the first conductor plate 104determines the amount of force that the first conductor plate 104applies to the second leg 106 b of the second conductor plate 106 at thefulcrum of the non-conductive portion 104 a. Because the first conductorplate 104 is effectively mounted to the rigid structure through themounting plate 114, the amount of force applied by the first conductorplate 104 determines the angle at which the second conductor plate 106rotates about the hinge 112.

The angle of rotation about the hinge 112 of either the second conductorplate 106 or the substrate 102 is determined by the degree of lengthwiseexpansion realized by the first conductor plate 104 and the amount ofbend (warping or bowing) realized by the first leg 106 a of the secondconductor plate 106, respectively. In response to an increase of theexternal temperature, the first conductor plate expands to thereby applya force to the second conductor plate 106 through the fulcrum of thenon-conductive portion 104 a. The amount of applied force determines theangle of rotation about the hinge 112 that is achieved by either of thefirst conductor leg 104 or the second conductor leg 106.

As the temperature nears ambient levels, the lengthwise expansion of thefirst conductor plate 104 also decreases. As the expansion decreases,the first conductor plate 104 returns to its initial state. The mountingspring 116 restores the temperature sensor 100 to its original positionby applying a force to rotate either the first conductor plate 104 orthe second conductor plate 106, depending on the mounting position, inan opposite direction about the hinge 112.

In some embodiments, the temperature sensor 100 is composed of metal andceramic materials that enable temperature measurements within a range ofapproximately 40° F. to 600° F., or lesser or greater as desired. Therange of temperature measurements is determined by the resiliency of thematerials along with the degree of expansion and the degree of warpageundergone by the conductor plates, respectively. The degree expansion ofthe conductor plate 104 is determined by the thickness and rigidity ofthe substrate 102. For example, the substrate 102 may be a single ormultilayered structure.

In an embodiment as shown in FIG. 2, the temperature sensor 100 includesthe substrate 102 which is a single piece formed from ceramic or anon-conductive, hard, durable material. In some embodiments, thetemperature sensor can be placed in a field container to protect thetemperature sensor from contamination, as the temperature sensor 100 maymonitor the temperature in a gas filled vessel or a liquid filledvessel.

FIG. 3 illustrates a system 300 for measuring temperature in anenclosure (E) of an embodiment.

The enclosure (E) can be implemented in numerous shapes and sizes, forexample, and can be implemented as a full or partial enclosure. Theenclosure, as illustrated, is a representation of a full enclosure thatis located below ground, such as a borehole or well, and contains aliquid or gas at a high temperature. The temperature of the liquid orgas in the enclosure may be measured at temperatures up to 600° F.

The system 300 also includes a high temperature generation unit 302which may, in operation, generate high temperatures in the enclosure(E). The high temperature generation unit 302 can be represented bynumerous industrial applications such as machinery used in drillingoperations, manufacturing operations, or construction operations forexample. One of ordinary skill in the art will appreciate that the hightemperature generation unit 302 can be represented by any heater.

The system 300 includes a signal generator/receiver 303 for generatingan electromagnetic signal, such as an RF signal or an electromagneticpulse (EMP), for example. The electromagnetic signal can be generated ina range of 3 Hz to 30 GHz, or any other range suitable to achieve thedesired response or to the environmental conditions.

The system 300 also includes a capacitive sensor 100 for establishing acapacitance based on the generated temperature. As shown in FIG. 1, thecapacitive sensor 100 includes a first conductor for generating amechanical force in response to the temperature generated by the hightemperature generation unit 302. The capacitive sensor 100 also includesa second conductor 106 configured to rotate about the first conductor asa result of the force generated by the first conductor 104. The amountof rotation of the second conductor 106 is determined by the forcegenerated by the first conductor 104. The capacitive sensor 100 can beincluded in a resonant circuit 304, where the change in capacitance ofthe capacitive sensor 100 shifts the frequency of a signal transmittedby a base station.

The resonant network 304 includes an inductor 306 that connects theresonant network 304 to an antenna 308. The antenna 308 can be anyelectrical device suitable for receiving or sending a radio frequency(RF) signal or a more generalized electromagnetic signal, e.g., such ascabling, conductive piping, or a coil. The resonant network 304 alsoincludes a network resistance 312 and a network inductance 314. Theresonant network 304 receives the RF signal through the antenna 308, and“rings” or resonates at its natural frequency. The capacitive sensor 100is configured to sense the temperature of the enclosure (E) and modulatethe vibration frequency induced in the resonant network 304 when the RFsignal is received by the antenna 308. The capacitive sensor 100modulates the frequency of the RF signal based on the size of the gap(G).

The system 300 also includes a correlator 316 for correlating themodulated frequency to a temperature value. Those of ordinary skill willappreciate that the correlator may be a processor, computer, or otherprocessing device located at a base station. The correlator 316 mayperform any desired processing of the modulated signal including, butnot limited to, a statistical analysis of the modulated frequency.Commercial products are readily available and known to those skilled inthe art can be used to perform any suitable frequency detection. Forexample, a fast Fourier transform that can be implemented by, forexample, MATHCAD available from Mathsoft Engineering & Education, Inc.or other suitable product to deconvolve the modulated ring received fromthe resonant network 304. The processor can be used in conjunction witha look-up table having a correlation table of modulation frequency—tosensed characteristics (e.g., temperature, pressure, and so forth)conversions.

FIG. 4 is a flowchart illustrating a method of measuring the temperatureof an enclosure in an embodiment. The method is executed using thecapacitive sensor 100 as described with respect to FIG. 1. As shown instep 400, a predetermined frequency electromagnetic signal, such as anRF signal or electromagnetic pulse, is generated by a base station andtransmitted to the resonant network 304 that includes the capacitivesensor 100. The capacitive sensor 100 modulates the receivedelectromagnetic signal based on the temperature of the enclosure (step402). Specifically, capacitive sensor 100 shifts the frequency due to anadjustment in the size of the gap (G), whereby at least one of theconductor plates of the sensor 100 undergoes a lengthwise expansion,which causes a rotation increase the gap (G) established between theconductor plates.

The resonant network 304 emits a signal having at the shifted(modulated) frequency of the conductor plates about a hinge to the basestation (step 404). The base station correlates the shifted frequency toa temperature value so that the observed temperature of the enclosuremay be determined (step 406).

While the invention has been described with reference to specificembodiments, this description is merely representative of the inventionand is not to be construed as limiting the invention. Variousmodifications and applications may occur to those skilled in the artswithout departing from the true sprit and scope of the invention asdefined by the appended claims.

1. A method of measuring temperature in an enclosure using a systemhaving a capacitive sensor with a first conductive plate and a secondconductive plate rotatably attached to the first conductive plate, themethod comprising: generating a signal having a predetermined frequencyspectrum; modulating the frequency spectrum of the generated signalbased on a relative rotation of the first and second conductive platesresponsive to a temperature in the enclosure; and correlating themodulation to a temperature value.
 2. A method according to claim 1,wherein the modulating comprises: generating a mechanical force based ona lengthwise expansion of the first conductive plate relative to thesecond conductive plate in response to the temperature in the enclosure,causing rotation of the second conductive plate about an axis of thefirst conductive plate to adjust a gap between the second conductiveplate and the first conductive plate, thereby altering a capacitance ofthe capacitive sensor.
 3. A method according to claim 2, wherein therelative lengthwise expansion results from the first conductive platehaving a higher coefficient of thermal expansion than does the secondconductive plate.
 4. A method according to claim 2, comprising:generating temperatures of between about 40° F. and about 600° F. in theenclosure.